The invention relates to a seat belt retractor of the automatic locking type and more particularly provides mechanism for delaying lock up of the retractor until the vehicle experiences an attitude change or an inertia condition of predetermined magnitude.
Conventional seat belt retractors employed in motor vehicle bodies have a spring biased reel which winds the seat belt to a stored position. The seat occupant may extend the seat belt by unwinding it from the reel and then engage a buckle member on the seat belt with a mating buckle member mounted on the vehicle body to fix the seat belt in a restraining position about the occupant. A locking device is provided which functions to limit unwinding of the belt beyond the extent at which effective restraint of the occupant is provided.
One well known locking device for a seat belt retractor is the so-called inertia locking device wherein the belt may be freely wound and unwound until an inertia sensing member is actuated by an inertia force of a magnitude which is indicitive of an unusually high rate of vehicle acceleration or deceleration.
Another well known type of seat belt retractor is the automatic locking retractor. In a retractor of this type, an automatic locking device is employed which prevents locking of the reel while the occupant extends the belt from a fully wound position and then permits a locking pawl to move into engagement with the reel when the belt is retracted. The pawl ratchets over the reel to permit progressive winding of the belt to a snug position about the occupant but will not permit unwinding rotation of the reel.
An advantage of the automatic locking retractor is that the locking function occurs without requiring conscious lock actuating effort on the part of the seat occupant. On the other hand, a disadvantage of the automatic locking retractor is that if the seat occupant inadvertently allows the belt to be retracted somewhat during the process of fixing the belt in its restraining position, the automatic locking device will lock the retractor against further extension. This is particularly frustrating to a seat occupant who is unfamiliar with the operation of an automatic locking retractor and requires that the belt be allowed to fully rewind on the reel before the belt can be again extended.